


Lacuna

by obstinatrix



Category: Supernatural
Genre: M/M
Language: English
Status: Completed
Published: 2011-06-14
Updated: 2011-06-14
Packaged: 2018-10-17 06:25:29
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,757
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/10588263
Author URL: https://archiveofourown.org/users/obstinatrix/pseuds/obstinatrix
Summary: It was all about Cas. That was the agreement, anyway.





	

**Author's Note:**

> So, a very long time ago, [](http://light-like.livejournal.com/profile)[light_like](http://light-like.livejournal.com/) made a very generous bid on me in the [](http://help-nz.livejournal.com/profile)[help_nz](http://help-nz.livejournal.com/) auction. Here, _finally_ , is your fic, bb. I'm sorry it took so long. I hope this works. ♥ NB: please note the pairing. Cas is in the middle but this fic contains incest all the same. Generic Season 5 spoilers.

**Title** : Lacuna  
**Pairing** : Dean/Castiel/Sam  
**Rating** : NC-17  
**Words** : ~4,000  
**Summary** : It was all about Cas. That was the agreement, anyway.  
**Notes** : So, a very long time ago, [](http://light-like.livejournal.com/profile)[**light_like**](http://light-like.livejournal.com/) made a very generous bid on me in the [](http://help-nz.livejournal.com/profile)[**help_nz**](http://help-nz.livejournal.com/) auction. Here, _finally_ , is your fic, bb. I'm sorry it took so long. I hope this works. ♥ NB: please note the pairing. Cas is in the middle but **this fic contains incest** all the same. Generic Season 5 spoilers.

It was all about Cas. That was the agreement, anyway: this was for Cas's benefit, at Cas's characteristically blunt request, and that was all there was to it, no complications and no awkwardness. Cas was their friend, and when Dean promised him he wouldn't let him die a virgin, he damn well meant it.

That, at least, was how they'd gotten started.

Twenty minutes and three discarded sets of clothing later, and Sam can't understand why the hell he'd let himself get into this under any kind of assumption of casualness. This is _Cas_ , after all, the most socially inept of all the angels, and just because he hadn't worked out the way his feelings ran didn't mean nobody else was obligated to pause long enough to lay it out for him in small words. This is _Cas_ , incredibly, whose skin runs sticky-smooth under Sam's palms, and the look on his face as his head tips back onto Dean's bare shoulder speaks volumes. Cas is large, Sam knows; he contains multitudes, he is as old as time, and yet the tightness between his brows, the gentle part of his damp slack mouth are perfect articulations of the same warm feeling shoving up behind Sam's breastbone, the sense of something swelling in him, bigger than his body can contain. Cas, Sam supposes, probably puts this down to the constraints of the human vessel, lesser than its endless capacity to feel, but Sam knows better. Sam knows this is the one thing that renders all Dean's 'casual sex' arguments invalid, and he can't understand why he didn't put his foot down before -- except that it would have entailed explaining himself to Dean. Explaining himself _and_ Cas, and potentially freaking Dean out for all eternity.

Now, though, he can't imagine Dean hasn't worked it out, unless he's a bigger fool than Sam realised. His hands are broad and flat on Cas's stomach, fingers curving firmly over the ridges of his hipbones, and Sam's shoulders tense at every minuscule shift, every sweep of Dean's thumbs. They're beautiful hands, or so he's always thought: long-fingered and deft, capable and large, and Sam wants to see them curled around Cas's cock; wants to make a tunnel of his own mouth and slide down to meet them.

Dean would never have taken this -- _thing_ so casually if he'd known just how far Sam's interest stretches, beyond the taut paleness of Cas's body and onto Dean's hands, the line of his throat, the sinful curve of his mouth. Cas is all kinds of hot between them, sure, his every stuttered sound of new-discovered pleasure stoking a bank of heat in Sam's gut. But Dean, behind him, is entirely absorbed in Cas, rutting leisurely against the small of his back, keeping this as normal as a threesome with your brother can conceivably be. He's beautiful in his abandon, sex-flush crawling pink and hot over the plains of his face, and Sam can't help but watch him as he draws his own mouth along the cut of Cas's pelvis; trails the backs of his fingers idly up the length of his cock. Dean is hot as hell and he knows it, knows Sam knows it, but Sam suspects he'd snap out of his haze of languid arousal if he realised just how much Sam wants to reach through Cas's legs and fist his brother's blood-warm dick.

Even the thought makes him shiver, slow crawl of heat between his shoulderblades, and Sam ducks his head as if the flush in his face might die down that way, the way dizziness recedes with inversion. He's built wrong, has always known it, but it wasn't supposed to come to a head like this, the three of them naked and breathless and Dean making soft sounds in his throat where Sam could almost stand up, unfold himself and swallow them, if he wasn't so afraid for his life. Fuck, this was never supposed to happen, and Sam's a goddamn fool for letting it.

 _Cas_ , though. The thing about Castiel is that, for all his awkwardness, he's shockingly persuasive when he wants to be, voice like dark gravel under fire, blue eyes hot and undeniable. Cas wanted this, asked for this, when he's never asked the two of them for anything, and something in Sam couldn't bear to deny him. Not when the crooked tilt of his head has been drawing Sam's eyes for a good many months, now; the sway of his hips when he moves, his soft wide mouth. The way Dean watches him is more than that, something deep and guarded, but more than once their eyes have met in looking at him, caught on the same slant of light through Cas's mussed hair, the same expression on his face, distant and feline and intriguing. Cas is something unearthly, beautiful, and the part of Sam that is twisted and burned cannot help but be soothed at the thought that he might want Sam's hands on him, this being of grace, Sam's mouth on his skin. The idea alone seemed enough of a benediction to make Sam forget about the complications; about how difficult it would be to watch Dean touch and yet not touch him; to put their hands and mouths on Cas together and yet not trespass onto each other's familiar skin.

Now, of course, it is too late. Sam's achingly, traitorously hard, the head of his cock leaving shiny smears of slick on Castiel's legs, on his own stomach, but this is for Cas, Sam on his knees before him, where he belongs. Above, Dean is kissing him, the soft drag of lips up the column of Cas's throat transmuting into something wet and obscene when Cas turns towards him and takes his mouth, slack and deep. The sound of it alone is enough to kick up sparks at the base of Sam's spine; he doesn't dare lift his eyes far enough to _see_ it, the slick flash of their tongues in the space between their mouths, the way their sharp lines blur so naturally together. In front of him, Cas's dick is twitching at the contact, precome pearling out of the slit, and Sam can _smell_ it, musky and raw; feels the pull at the back of his throat that wants to be closer; wants to wrench a sound of his own out of Cas's mouth, let Dean swallow it and lick away the traces.

 _Shit_. Sam's fingers shift reflexively on Cas's hips as the thought of it hits him like a punch to the gut, the imagined jerk of Cas's head, the choked-off cry. Cas's hands in his hair, tangling, fisting. He can almost feel the tingle in his scalp, vibrating through his jaw, and Cas is so close, the shallow of his stomach sheened with sweat over the suggestions of muscles. Sam's eyes close of their own accord as he leans in, rubs his open mouth over the spur of Cas's hip, an inch below Dean's cradling hand. "Cas," he murmurs, involuntary; licks the word from Cas's skin with the flat of his tongue until Cas shivers, stomach leaping at the touch.

It's nothing, after that, to shift a little further, curl his tongue around the head of Cas's cock where it's slick and glistening. Cas's moan seems to break from the very depths of him, and Sam feels his heart pick up in his throat, thundering in his jaw as he mouths at Cas gently, lets his lips go slack after a moment to take the first few inches of him in. Cas shivers, hips hitching up, the head of him jolting uncomfortably against Sam's soft palate, but the sound he makes at the contact is worth it; the way his fingers curl on Sam's neck, sliding upward into his hair. Beyond, Dean murmurs something wordless and soft by way of response, one hand slipping away from Cas's hipbone with a whisper of skin. Sam shifts his own hand upward reflexively, thumb digging into the place still white where Dean gripped it, and pulls Cas in, lifts his head and shoves down again, re-angling it until it works.

It's obvious, the moment he gets it right. Cas's voice rises sharply, almost pained, as the tip of him nudges the back of Sam's throat, as Sam swallows around him, adjusting. He's bigger than Sam expected, and this is harder than Sam remembers, but then, the last time was loosened by tequila, by the low buzz of music and the casual permissiveness of a college party. This is something entirely different, tense with the clench in Sam's stomach that sings disbelief, that wants to take all of Cas inside himself until he is clean. Cas's hand is tight in Sam's hair, aching along the scalp, but the pain is something dull and pure, and Sam wants more of it. He pulls off slowly, sucks at the crown and descends again, and this time, it is easier. Cas's hips stutter, cock pulsing a slick of bitterness over the back of Sam's tongue, and Sam swallows it; licks a flat stroke up the underside and sucks harder until Cas jerks again, establishing a hesitant rhythm as he pushes into Sam's mouth.

Two strokes, three, and Sam is lost it in it, his absorption unexpected and complete, throat relaxing to let Cas in. There's something bizarrely hot about the way it burns, the ache in Sam's jaw and the full-body effort it takes to suppress his panic reflex long enough for Cas to fuck in deep, full-length and hard into the tight, slippery clench of Sam's throat. His eyes water with the effort, but Cas is moaning above him, shivering all over his skin, and the spark of adrenaline is somehow everywhere, roaring in Sam's ears, chemical burn of it pounding in his blood. It occurs to him, as Cas twitches in his mouth, slides slickly against his cheek, that this is what he's wanted; that maybe Dean was right, whether he understood why or not. This is Cas, agent of God's grace, taking what Sam offers, and the rush of it is involving enough that Sam can almost forget what came before. This is _Cas_ , loose and human and undone, and Sam is doing it, to him and for him. The thought makes him groan around the intrusion, around the thick weight of Cas sliding musky and sharp on his tongue.

For long moments, the claustrophobia is almost enough, Sam's cock growing fat and slick against his thigh as Cas grips his hair, fucks him deep. Then Cas's voice breaks on a gasp, hips torquing strangely, breaking the rhythm, and Sam remembers. _Dean_. He pulls off, wet and slow, taking stock as he pushes his tongue into the slit at Cas's crown. Cas shivers, hisses his response, but his stance is wider, now, thighs spread, and there are Dean's deft fingers making circles between.

The sudden rush of saliva makes Sam's cheeks cramp, a bolt of heat shooting through him in a way that throws up dark spots in his vision like vertigo. Dean's _fingers_ , and Sam wants to pull off, shoulder his way in between Cas's thighs and work his tongue in around the tips of them, slick them up so the two of them can fuck Cas open together. He wants it so viscerally, the urge so fiercely direct and clear that, for a moment, he almost thinks he's done it. Then Cas moans, cants his hips, and Sam sees the stretch as Dean's fingers shove inside of him, the tight pink clench of Cas's body. "Shit," he breathes, lips gone slack around the tip of Cas's cock, "shit, Dean."

It's a breach of their unspoken etiquette, flagrantly, but nobody remarks on it, Dean hitching a breath into the hollow of Cas's throat where he's raising a bruise, Cas's hand tightening in Sam's hair, half-conscious flex of fingers. Sam's far enough gone, mind gone loose in the heat skidding through him, that it reads like permission, Cas's little snatches of breath becoming closer to sobs as Dean's fingers twist inside him, the jagged thrust of Dean's pelvis bringing the three of them flush together. It's reckless, Dean's beautiful hands still Dean's, still Sam's _brother's_ , after all, but Dean has said nothing and Sam's only human, maybe less than, and it's more than he can do to pull back.

Cas is half off the ground, now, body tilted back onto the pan of Dean's pelvis, and his legs splay easily when Sam slides his palms up the insides of his thighs, ducks his head to nuzzle at the base of his cock. So easy to lift him, to take the rest of his weight so he's balanced on his toes and everything he is is supported between them, and Sam is so _close_ now, mouthing at the weight of Cas's balls. The sounds Cas makes are low, animalistic. Sam chases them with his tongue, tracing a hot line along the sensitive stretch of Cas's perineum. In his peripheral vision, Dean's fingers work like a piston, long smooth strokes that Cas pushes into in blind encouragement.

It shouldn't be as easy as it is just to keep on moving, to trail his tongue over Cas's stretched rim and into the shadowed place beyond. It shouldn't be easy, but Sam is caught up in the momentum of it, the way Cas shudders between them, Dean's low, soft groan when Sam tongues at his fingers, hot and wrong and simple. For a second, as Sam fucks his tongue into the space Dean's made for him, they're collaborators, still _just_ in the hinterlands of the acceptable. The heat of it is arrowing down between Sam's legs, but Dean doesn't have to know; doesn't have to turn this into something they can't back down from afterwards. And then Dean shifts, withdraws his fingers slow and shining, and Sam's breath catches in his throat, heart stilling in his chest.

"Sam." Dean's voice is like broken glass, sex-roughened and indelible. "Come on, _Jesus_." And then his fingers are teasing at the curve of Sam's lower lip, pushing in to touch the wet hot inside of his mouth, and Sam is done, _shit_ , Sam's finished. " _Sam,_ " Dean repeats, and it's all Sam can do to breathe before he's turning his head, opening his mouth to let Dean fuck two fingers to the back of it, firm over the flat of his tongue.

After that, it is as if the world disintegrates. Sam's heart is pounding in his ears, in his head like waves or wind, and Cas is suddenly heavy between them, Sam's arms giving way where they're holding him steady. "Hey," Dean murmurs, gentling, "hey," and then they're laying Cas down, spreading him flat on the worn motel carpet. Cas makes a soft sound of protest, lifts his hips. Dean laughs and pushes two fingers back into him, wet and glistening now with Sam's spit.

"Jesus, Cas," he says, "I was on it." His voice is so entirely, so unquestionably _Dean_ that Sam feels all tangled up inside at the sound of it, so familiar in this utterly unheard-of situation. "What'd you want, huh? Want Sam's mouth?"

"Want your cock," Cas shoots back, not missing a beat, and it hits Sam like a blow, the borrowed word in Cas's crushed-velvet voice, the way he pushes back onto Dean's fingers.

"Shit," Dean hisses through his teeth, and Sam is gratified to note that he sounds as wrecked as Sam feels, the muscles in his forearms trembling finely from elbow to wrist. "Tell us how you really feel, why don't you."

"You asked," Cas points out, the words blurring into a groan in his throat as Dean withdraws his fingers, spreads Cas's thighs with his palms. Between, he is open and ready from Dean's ministrations, and Sam feels his own jolt of arousal echoed in Dean, sparking like electricity across the distance between them. Then, without warning, Cas is pulling himself up on his elbows; rolls over and up onto his hands and knees on the carpet.

"Uh," Sam says, dry and tight. Cas throws him a dark-eyed glance over his shoulder, one eyebrow raised pointedly.

"Sam," he says, soft and sure, "come here."

The knobs in Cas's spine stand out, shadowed on his skin, right down into the dip at the small of his back where Sam wants to bury his face, his mouth. He shivers, involuntary; runs fingers up the back of Cas's thigh, and then he's moving, ungainly and staggered on his knees. Cas seems to have no objection, eyes steady, mouth damp and parted. As he draws up level with Cas's shoulders, Cas shifts his weight onto one hand and reaches out an arm to haul him in, palm flattening low on Sam's back. "Sam," he murmurs, and rubs his mouth against the jut of Sam's hipbone, his cheek against Sam's cock. Sam's hands fly out automatically to cup Cas's jaw, grip his hair, and somewhere on the edges of his consciousness, Dean draws in a disbelieving breath.

"Fuck," he whispers, "fuck."

Sam has to look up at him, then, has to see his face as he tugs at Cas's hips, brackets him with both hands, shoves inside. He's beautiful, desperate; and his eyes lift to Sam's as Sam watches, setting Sam's pulse racing frenetically in his throat. Dean, by rights, should be repulsed by Sam's attentions, but the evidence is overwhelmingly, shockingly against it. He pulls out deliberately -- fucks forward again, little staggered thrusts -- and doesn't look away; only watches Sam as his eyes go dark, mouth falling open. When Cas breaks into Sam's consciousness, mouthing clumsily at his cock, Sam feels it everywhere, wet and messy, filthy and glorious.

"Shit," he rasps, " _Cas -_ " and Dean is watching him, eyes gone green as glass as his fingers wrap around Cas's waist, sweat licking a path down his breastbone as he moves. His hips work slow at first, but the heat between them is spiralling, every thrust shoving Cas a little further onto Sam's cock, drawing a cry out of him and Sam both. As if Dean were fucking them both together, the three of them one inside the other in an endless cycle that shouldn't be so filthily perfect.

"Cas," Sam repeats, weakly, and rubs the pad of his thumb over Cas's smooth cheek, the ridge of his cock palpable beneath the skin.

He doesn't know what makes Dean move, what secret parallel drive sets the sense prickling through him that the circuit is incomplete. Left to himself, Sam never would have done it; would only have closed his eyes and clutched at Cas's shoulders and counted himself blessed. Dean, though, is reckless where Sam is cautious, subject to his blood and his gut, and somehow it's as characteristic as it is startling when he reaches forward over the length of Cas's back to grip Sam's nape, hauling him forward until their foreheads touch.

"Dean," Sam manages, the word startled out of him even as his palm comes to rest on Dean's cheek. Dean only laughs, hips snapping forward in an easy rhythm, breath warm and damp on Sam's open mouth.

"Sssh," he breathes, warm and low, and then his mouth is on Sam's as if it were nothing; as if it were as obvious and as easy as breathing. Dean tilts his head, presses in until they're kissing open-mouthed, slow and wet and tasting of Cas. Between them, Cas groans, shoves back as if he knows, encouraging and wanton, and like that, Sam hits overload, terminal velocity, mouth going slack against Dean's.

"Fuck," he rasps; jerks forward into Cas's mouth and stills, body pulling taut and close and shivering. " _Fuck_ ," and he's coming in spurts, long and hard against the back of Cas's throat as Cas swallows around him, working him through it as if he'd done this before; as if he isn't just putting his angelic superiority to the most blasphemous of uses.

As in any circuit, the dissolution of one component seems to spark a chain reaction, a push-pull of action and reaction within which Sam is suspended like light. Dean fucks forward, hips stuttering, and Cas is moaning before Sam is even done coming, back arching as he spurts over Dean's fist.

"Christ," Sam murmurs weakly, collapsing back onto his heels, and Cas half-laughs, low and abrasive through the burn of his throat. It's shamefully hot, the smoker's rasp of it; and hotter still when Dean's palm finds the back of Cas's head, shoving it down as his thrusts speed aggressively on the edge of climax. Cas is spent, arms trembling, but he holds up manfully as Dean fucks into him, hauling him backward onto his cock.

"Cas," Dean grits through his teeth, fingers white-knuckled in Cas's hair, desperately seeking traction as he jackhammers into him. "Cas, _shit_ ," and his hips snap forward, stilling for a long, tense moment before he comes. Beneath him, Cas can only moan, slipping forward onto his elbows, and Dean is too wrecked to do anything but follow, face pressed damp to the hollow between Cas's shoulderblades.

At some point, Sam thinks, they will have to talk about this. At some point in time, the apocalypse will be a fading memory and crimes against God will loom large on their radar once again as pressing concerns. For the time being, though, Sam is too bodily exhausted to be anything but grateful when Dean pulls him down, pulls him in; when Cas snakes an arm around his waist. For now, they're fucked out and breathless and satisfied, and maybe it's screwed up that it's all they have, but that doesn't make it any less true. Dean is a boneless heat under Sam's arm, Cas wrecked and happy between them, and Sam doesn't want to question it. Frankly, for the moment, he refuses. Maybe they'll talk about it after the apocalypse, if any of them live that long.

Maybe. Sam's making no more promises.


End file.
